1. Field of the Invention
The present invention relates to improvement in reliability of a semiconductor cooling device which cools a semiconductor chip mounted in a power semiconductor device used for a power converter, a switching power supply or the like.
2. Description of the Background Art
A capacity of the power semiconductor device used for the power converter, the switching power supply or the like is on the increase year by year, and a semiconductor chip (e.g., IGBT (insulated gate bipolar transistor)) mounted in the power semiconductor device is electrified and used with a higher current density, whereby there have been challenges of taking a heat radiation measure and extending a power cycle life. In particular, development of a semiconductor device is recently proceeding, the device being operated at a high speed by use of a compound semiconductor (SiC, GaN, etc.) with a high heatproof temperature for a semiconductor element, and a heat radiation measure therefor is becoming increasingly important.
For example, Japanese Patent Application Laid-Open No. 2007-67228 discloses a circuit board where a cooling medium channel (cooling medium flow channel) is provided inside a board mounted with a semiconductor chip and the board is cooled by use of a cooling medium that flows through the cooling medium channel to cool the heated semiconductor chip.
However, in the circuit board described in Japanese Patent Application Laid-Open No. 2007-67228, every region of the cooling medium flow channel provided inside the board is uniform, and hence a temperature of the cooling medium becomes higher in an outlet-side region of the cooling medium flow channel than in an inlet-side region thereof, thus generating a difference in temperature of the cooling medium between the inlet-side region and the outlet-side region. For this reason, the semiconductor device including the semiconductor chip cannot be uniformly cooled, thereby causing problems such as a problem of increasing a difference in thermal stress based on the temperature difference in the semiconductor device to shorten a power cycle life of the semiconductor device.